There are 3 US Post Offices in Alamosa County serving a total of 15,467 residents equating to 5,156 residents per post office. It's estimated that approximately 24,687 packages are handled across the 3 county post offices annually. Alamosa County is one of the 64 counties of the U.S. state of Colorado. As of the 2010 census, the population was 15,445. The county seat is Alamosa. The county name is the Spanish language word for a \"grove of cottonwood trees.\""